PB2628: EXPERIENCE AT THE GUADALAJARA UNIVERSITY HOSPITAL (SPAIN) IN FETAL AND NEONATAL ALLOINMUNE THROMBOCYTOPENIA (FNAIT) DURING EIGHT YEARS.
Authors: María Irene Nuevo López, Marta Mora Argumanez, Mª Dolores Morales Sanz, Rocio Perez Alonso, Beatriz Álvarez Padilla, Ángela Gil Pérez, Helga Guillén García, Alejandro Vazquez Ramo, Berta Mercedes Michael Fernandez, Nuria Golbano López, Sonia Herrero, Jaime Arbeteta Juanis, Dunia de Miguel Llorente
Journal: HemaSphere (2023)

Topic: 32. Platelet disorders Background: Main cause of severe thrombocytopenia in healthy, full-term and first-born neonates born to a healthy mother with normal platelets (plaq), no history of coagulopathy, drug intake, or immune disease is FNAIT. Underdiagnosed disorder with 1 in 5000 live births. It consists of a maternal-fetal plaq incompatibility, maternal alloimmunization against fetal human plaq-specific antigens (HPA), inherited from the father, and of which the mother lacks. Crucial early diagnosis and ante or postnatal management for avoiding severe bleeding complications (intracranial hemorrhage (ICH)) Aims: Analyse clinical-therapeutic characteristics of FNAIT cases in a tertiary level hospital, with approximately 1600 deliveries per year. Methods: Descriptive and retrospective analysis carried out at Guadalajara University Hospital from January 2015 to February 2023, through clinical, analytical and transfusion data recorded in computer system and filed on paper. Laboratory tests used: Pak Lx assay (Luminex qualitative immunoassay), genomic typing of platelet antigens, serological typing, and crossmatching of maternal plasma with parental plaq and donor isogroup HPA-1a. Results: 5 cases of FNAIT were collected from 4 healthy Caucasian pregnant women, having had 9 pregnancies. Demographic characteristics and management described Table 1. The principal cause (80%) for searching and study FNAIT are haemorrhagic mucocutaneous lesions and postnatal thrombocytopenia, followed by 20% personal history (previous child with confirmed FNAIT). In 3 patients (75%) presence of antiplaq antibodies (ab) in maternal serum with anti-HPA-1a specificity, 1 of them also presented anti-HLA class I. Genetic typing; 100% HPA-1b+ homozygous mothers. In 3, their partners were homozygous HPA-1a+ gene typing and in 1 was heterozygous HPA-1ab+. In the case of heterozygous HPA-1 couple, previous pregnancy without FNAIT and the patient did not present positive antiplaq ab. Another couple, homozygous HPA-1b pregnant and homozygous HPA-1a male, only 2nd parturition with dg FNAIT. Only 1 pregnant receives antenatal treatment in her 2nd pregnancy for previous FNAIT; Igs 1g/Kg/week from week 20, a total 16 doses until peripartum. Serial measurements of antiplaq ab until negative result (week 31). Scheduled normal delivery and normal plaq counts. The other 4 newborns received an average of 1 (RI 0.75-2) pools of plaq and 2 (RI 2-2.25) Igs at a dose of 0.5-1 g/kg/day for severe thrombocytopenia. The ones who received 1g/kg Igs show prompt platelet count recovery. Negative ultrasound screening for ICH. Summary/Conclusion: FNAIT is confirmed as rare disease by incidence rate 4% in 8 years. We present 5 FNAIT cases in 4 pregnancies. Finding of Antiplaq HPA-1a and anti-HLA I ab combination were described in the literature, 37-45% cases. It is confirmed low immunization rate in 1st parturition, only 10% pregnant women with antiHPA-1a+ ab develops FNAIT (as literature). Antenatal treatment based on Igs +/- prednisone avoids the severity of thrombocytopenia and ICH in successive pregnancies. Adequate postnatal therapy is needed to avoid comorbidities with high morbi-mortality, using from specific HPA-negative plaq tx to polyspecific Igs 1g/Kg/d x 2 days.Keywords: Cerebral hemorrhage, Fetal, Immune thrombocytopenia (ITP), Neonate